In certain control systems, such as in speed regulation apparatus for mass and/or rapid transit operations, it is common practice to convey the various speed commands to the vehicle or train via cab signaling. Normally, the cab signal command signals take the form of coded carrier waveform wherein the code rate determines the given permissible speed or velocity that the vehicle or train is to travel within the particular block or track section. The coded or modulated speed command signals are inductively coupled from the wayside or track rails to the vehicle through suitable magnetic pickup devices. The picked-up modulated carrier signals are amplified, demodulated, shaped, limited and are then applied to an appropriate decoder, such as a relay decoding logic unit. In a semiautomatic cab signaling system, a trainman or engineer manually operates a master control handle to either increase or decrease the speed of the vehicle and train preferably in accordance with the received cab signal speed commands of the given block or track section along the route of travel. In keeping with the operating standards, it is necessary to compare the digital contact position of the operating handle with the digital output of the cab signal relay logic network in order to ensure that the vehicle is traveling at the most restrictive speed. That is, when a disagreement occurs between the speed position of the contact handle and the speed command of the relay logic decoder, it is a basic requirement that the vehicle operate at the lesser of the two speeds in order to maintain a high degree of safety. In addition to determining the most restrictive of the two speeds, the digital inputs must be converted to an analog signal for subsequent use by the cab signal control equipment for effectively regulating the speed of the vehicle or train of the mass and/or rapid transit system.